Influence of the Topological Structures of the Nose of High-Speed Maglev Train on Aerodynamic Performances

In the past few years, considerable attention has been paid to high-speed maglev train in the field of rail transit. The design speed of the high-speed maglev train is 600km/h, which is significantly higher than that of the high-speed train. With the increase in operating speed, high-speed maglev trains have higher requirements for aerodynamic shape. Superior performance, the beautiful aerodynamic shape is an important direction for the development of high-speed maglev trains. Based on the Vehicle Modeling Function (VMF) method, the current research has developed a parametric shape design method suitable for the aerodynamic shape of the maglev train’s nose. This method can obtain different topological structures of the high-speed maglev train’s nose. The current research uses this method to generate four maglev train noses with large appearance differences and uses these train noses to construct four simplified high-speed maglev models. Then this study numerically analyzes the flow fields of different train models and compares the differences in aerodynamic performance including aerodynamic drag, aerodynamic lift and wake characteristics. The Q-criterion is used to study the vortex structure and mechanism of different train wake regions, and the vortex propagation process is studied by turbulence kinetic energy (TKE). Studying the difference in the aerodynamic force of different topological shapes will help to improve the aerodynamic performance of high-speed maglev trains.

Parametrization of High-Speed Train Streamline Shape

In the past decade, the high speed trains (HSTs) in China have experienced a booming development, with the design of CRH380A as a predominant example. A series of brand new HSTs have been developed with high aerodynamic performance, which includes the running resistance, the lift of the trailing car, pressure waves when trains pass by each other, aerodynamic noise in the far field, etc. In order to design HSTs with better aerodynamic performance, it is necessary to perform aerodynamic shape optimization, especially to optimize the streamline shape of HSTs. Parametrization is the basis for the whole optimization process, since good parametrization approach not only affects the optimization strategy, but also determines the design space and optimization efficiency. In the present paper, a series of work related to the streamline shape parametrization performed by the author in recent years have been introduced. Four different parametrization approaches have been exhibited, which are Local Shape Function method (LSF) and Free-Foam Deformation method (FFD), Modified Vehicle Modeling Function method (MVMF), Class function/Shape function Transformation method (CST). These methods could be categorized into two kinds: shape disturbance approach (LSF and FFD) and shape description approach (MVMF and CST). Among these four methods, some are developed by the authors while some are locally modified so as to meet the parametrization of the streamline shape. The detailed process of these four approaches are exhibited in the present paper and the characteristics of these four approaches are compared.

Development of a Vehicle Modeling Function for Three-Dimensional Shape Optimization

Representation of a complex three-dimensional (3D) shape requires extensive computer-aided design data consisting of millions (or tens of millions) of approximated discontinuous points. The quantity of data makes it difficult or impossible to efficiently optimize the entire shape. We present a vehicle-modeling function in the form of an exponential function to smoothly express the complex two-dimensional and 3D curved shapes of an automobile. This modeling function can modify and optimize the shape with fewer design variables compared with ordinary point-fitting methods. The subsectional parts of the vehicle-modeling function are defined as section functions by classifying each subsection of the automobile configuration as a section box model. The proposed approach is suitable for remodeling existing automobiles and for newly designed automobiles. The entire 3D aerodynamic shape of an automobile can be created using a set of the proposed modeling functions, which define a combination of section boxes. A 3D aerodynamic shape was developed to verify that the optimization of the shape was practical. This capability may help to reduce the developmental time or cost of automobiles and similarly complex systems. In addition, the proposed approach can be expanded to other fields of engineering.